Decision journal: what it is and why it matters

4.4.1 Why notes beat memory

Here is the uncomfortable arithmetic. Over 80 weeks you will study ~76 companies, work hundreds of problems, and read a dozen serious books. Two years after any module, your unaided memory of it will be a smudge. That isn't a personal failing. Memory works that way for everyone. Analysts who compound, like the Mungers with their latticework and the fund managers with twenty years of company files, do not have better memories. They externalized their thinking into a system that accumulates, so every new company they read collides with every old one. Sönke Ahrens' How to Take Smart Notes supplies the design. It describes the Zettelkasten method, built on sociologist Niklas Luhmann's 90,000-card slip-box, and your job today is a 90-minute installation.

Five design principles are non-negotiable:

Plain text. Markdown files are searchable, carry no lock-in, and will still be readable in 2056.
Atomic: one idea per note.
Your own words. Transcription is not understanding, and writing as if explaining to someone is the test.
Linked. A note's value lies in its connections, and links surface the cross-domain patterns that folders hide.
Fed by every module. Each module's final section prompts notes, and the system dies only if you stop feeding it.

For tooling, Obsidian (https://obsidian.md, free for personal use) is the recommended editor, since it renders [[wikilinks]] and draws the link graph. The system is deliberately tool-agnostic, though. Any text editor over a folder of .md files works. Your folder is the system. Keep two copies at minimum, a live folder on cloud sync plus a monthly zip elsewhere. Losing this folder in year 3 would be the most expensive accident available to you, so set the backup up today.

4.4.2 The three note types and the workflow

Ahrens distinguishes three kinds of note. Fleeting notes are anything captured in the moment, such as "why does HUL spend 9% on ads?", dropped into the inbox. You process them within 48 hours and then delete them. Literature notes are brief summaries, in your own words, of what a source said, kept with the reference. Permanent notes are the product. Each holds one distilled idea, written as a standalone claim and linked into the web.

Your daily flow takes ten minutes at day's end. Empty the inbox, write 1–3 permanent notes, and link them. Twenty notes a day is not the aim. Two good ones is. Luhmann averaged six.

4.4.3 What "atomic" looks like

Take this passage from the orientation teaching: "Value is created only when a company earns returns on invested capital above its cost of capital and can reinvest at that spread; growth without the spread destroys value." A bad note copies the sentence. It's tempting, and it teaches you nothing. A good permanent note is titled with the claim, argues it in your words, attaches a number, and links out:

# Growth only creates value when ROIC beats the cost of capital
ID: 202607141020 · Tags: #valuation #roic #five-questions

A company that reinvests at returns below what its capital costs is
running a machine that turns ₹1 into 90 paise — faster growth just
runs the machine harder. Growth is an amplifier, not a virtue: it
amplifies the spread between ROIC and WACC, whichever sign it has.
So the second of the five questions ("is this a good business?") is
really: is there a spread, and how long can it last?

Example to self: a firm earning 8% on new projects when its capital
costs 12% loses 4 paise per rupee reinvested — growing at 30% makes
that *worse*, not better.

Source: M0.01 §the-five-questions
Links: [[202607141025-wacc-is-an-opportunity-cost]] ·
[[202607141030-the-five-questions]]

The title is a full-sentence claim. That makes it searchable, and it argues something. Its ID is a timestamp, which stays stable even if you rename the note. Its body is your words plus one concrete number, and there is at least one link. That's the atom. Thirty of these, each linked where the link is real, will outperform three hundred pages of highlights. Highlights are the collector's fallacy, the feeling of acquisition standing in for the work of understanding.

4.4.4 The folder tree: create it now

analyst-brain/
├── 00-inbox/          # fleeting notes; emptied within 48h
├── 10-notes/          # permanent atomic notes (the Zettelkasten)
├── 20-companies/      # one markdown file per company, forever
├── 25-filings/        # downloaded ARs/10-Ks/transcripts, one subfolder per company
├── 30-sectors/        # sector playbook notes (filled from Phase 5)
├── 40-checklist/      # master-checklist.md + mistakes-log.md
├── 50-journal/        # decision journal; one file per entry
└── 90-templates/      # the four blank templates below

Every file in the tree is plain markdown carrying the .md extension. Permanent notes are named 10-notes/YYYYMMDDhhmm-short-slug (e.g., 202607141020-growth-needs-roic-above-wacc), company files 20-companies/titan, and journal entries 50-journal/2026-07-14-hul-volume-prediction. Use lowercase and hyphens, with no spaces. Resist the urge to add folders. In a Zettelkasten the links do the organizing, and folders are just parking. If you're debating taxonomy for more than five minutes, you're procrastinating with extra steps.

4.4.5 Template 1: the permanent note

Save as 90-templates/permanent-note:

# <The claim, as a full sentence>
ID: <YYYYMMDDhhmm> · Tags: #<topic> #<topic>

<The idea in your own words. 3–10 sentences. Write it as if
explaining to a colleague who missed the class.>

<One concrete number, example, or company that makes it real.>

Source: <module/book/filing, section or page>
Links: [[<related-note>]] · [[<related-note>]]

4.4.6 Template 2: the company file

Keep one page for every company you ever touch, cumulative for life. At week 3 you can truthfully fill only the snapshot and the open questions. Everything else fills in as the program teaches you to see. Save as 90-templates/company-file:

# <Company Name>
Tickers: NSE <___> / BSE <___> or NYSE/Nasdaq <___> · CIK/scrip: <___>
Filings: <link to screener page / EDGAR company page>
First studied: <date> · File status: <skeleton / working / deep-dived>

## What it does (one sentence)
<Plain words. If you can't write this, stop and find out.>

## Business model & revenue engine        [fills from Phase 4]
<How ₹1/$1 of revenue is earned and what it costs to earn it.>

## Key numbers (update each pass)         [fills from Phases 1–2]
| FY | Revenue | OPM % | PAT | ROCE/ROIC % | CFO | FCF | Net debt |
|----|---------|-------|-----|-------------|-----|-----|----------|
Source + date for every figure: <filing, page>

## Moat hypothesis & evidence             [fills from Phase 4]
## Top 3 risks                            [fills from Phase 2 on]
## People: management / promoter / incentives   [Phases 2, 8]
## Valuation notes: what is the price implying? [Phase 3 on]
## Open questions
- <the things you cannot yet answer — the most valuable section>

## Log (append-only)
- <date>: <what you did/learned in one line>

4.4.7 Template 3: the checklist seed

Your investment checklist has one governing rule. It comes from aviation, by way of Atul Gawande, and from the investors Mohnish Pabrai and Guy Spier, who built their checklists by autopsying other investors' documented losses. Put plainly, an item earns its place only by pointing at a real mistake, either yours or a documented disaster. A checklist of borrowed platitudes ("buy good companies!") checks nothing. Save it as 40-checklist/master-checklist. The program seeds it with six items, and you'll meet the mistakes behind them properly in Phase 2's forensic case files:

# Master checklist (grows ONLY from logged mistakes)
Rule: every item carries (a) the failure it guards against,
(b) the date added. Review quarterly; merge, never delete.

- [ ] Can I explain how this company makes money in two plain
      sentences? — guards: complexity hiding rot (Enron). added 2026-07
- [ ] Did operating cash flow track reported profit over 5 years?
      — guards: paper profits (Satyam; Manpasand). added 2026-07
- [ ] Are receivables or inventory growing much faster than sales?
      — guards: channel stuffing / fake sales. added 2026-07
- [ ] What % of promoter holding is pledged (India)? — guards:
      forced-sale spirals (Zee, CG Power). added 2026-07
- [ ] Did I read the auditor's opinion — and check for auditor
      resignation? — guards: the auditor knew (Satyam; Manpasand;
      IL&FS group). added 2026-07
- [ ] Are there material related-party transactions? — guards:
      value tunneled out of minority shareholders' reach (IL&FS,
      DHFL). added 2026-07

Its companion is 40-checklist/mistakes-log. Every graded miss in the program gets one line there, whether it's a failed gate, a wrong practice answer that reveals a pattern, or later on a bad journaled call. Each line records the date, what happened, the root cause, and either the checklist item it spawned or "no rule yet." Think of the checklist as the distillate and the log as the mash.

4.4.8 Template 4: the decision journal

Why keep a journal at all? Because memory is a revisionist. Once outcomes arrive, your brain rewrites what you believed and why. That's hindsight bias, and it destroys the only data that can calibrate you. Your defense is mechanical. Write the entry before the outcome, include a falsifiable prediction with a confidence percentage, set a review date, and never edit, only append. The fields are fixed program-wide, and the app's journal uses the same schema. Save it as 90-templates/journal-entry:

# Decision: <one line>
Date: <YYYY-MM-DD>

**Decision.** <What exactly you are deciding/predicting — one
falsifiable sentence.>

**Thesis.** <WHY — three sentences maximum. If it takes more,
you don't understand it yet.>

**Disconfirming evidence.** <The strongest CURRENT facts against
you — sought honestly, stated fairly.>

**Base rate.** <The outside view: how often does this kind of
thing work out, for the reference class — not for you specially?>

**Confidence: <NN>%** <that the decision proves right by the
review date, as defined in "Decision.">

**What would change my mind.** <Specific, observable triggers —
"if X falls below Y" — decided NOW, while you are sane.>

**Review date:** <YYYY-MM-DD>

---
## Review (append-only; add at review date)
Outcome: <what happened>
Process score (0–2): <did I follow my own process?>
Calibration note: <was NN% honest?>
Lesson → mistakes-log / checklist: <link or "none">

Two of the fields need unpacking, because they're the only new concepts of the week.

Base rate, the outside view. Before you ask "will this work?", ask "how often does this kind of thing work?" Say you predict that a mid-cap will compound earnings 25% a year for a decade. Its story, the inside view, may feel compelling. The reference class asks what fraction of all listed companies ever sustained that, and the answer is brutally thin: low single digits. Starting from the base rate and adjusting beats starting from the story every time humans have checked. Kahneman's planning-fallacy work shows it, and so does Mauboussin's Base Rate Book, a Phase 6 companion. At week 3 your base rates will be rough guesses. Write them anyway. It's the habit you're building.

How does confidence calibration work?

Confidence % and calibration. "Fairly sure" can't be falsified, but "70%" is a claim you can score. A calibrated judge is right about 70% of the times they say 70%. Your first ten entries, and later the app's calibration dashboard, will show whether your 80%s are really 55%s. It's a humbling discovery, and it's worth more than any single correct call. For now the journal fills with process decisions and study predictions, and trades stay out of it. That's by design. You calibrate the instrument on cheap decisions before it prices expensive ones, and the decision-journal worked example shows a full entry.

Decision journal